My copending application Ser. No. 581,085 filed Feb. 17, 1984 and assigned to the assignee of the present application describes a document scanner employing a fiber optic bundle. (The above-identified patent application is incorporated herein by reference.) The bundle has a linear entrance face and a rectangular exit face. The positions of the fibers in the two faces not only are unknown but they bear no predetermined relationships to one another. In other words, the fiber bundle is non-coherent. The fibers at the entrance face, however, are constrained into a linear geometry and the fibers of the exit face are merely gathered randomly into the proper geometry to mate with the desired sensor array or arrays.
The fibers at the exit face are energy coupled in fixed positions with respect to a sensor array which is conveniently an optical random access memory (RAM) or a random access charge injection device (CID). The bundle is made coherent electronically.
Electronic coherence is achieved during an initialization process by moving a beam of light, small compared to the fiber size, in increments along a path at the entrance face which intersects all the fibers in sequence. A software program is operative to store all the addresses of the sensors illuminated for each position of the beam. The software also is operative to determine when maxima occur in the number of illuminated sensors as the beam is moved. The address of a single sensor is selected out of the group of illuminated sensors for each maximum. The sequence of addresses thus identified is reduced to one sensor address per maximum and their address is taken as corresponding to the exit position of a fiber.
In normal operation, a permanent memory is adapted to interrogate only the single sensor at the stored address for each fiber, in the sequence in which it was stored, each time a line of the document is scanned. Thus, only a small subset of the sensor array is addressed leading to high speed operation. It is clear that a non-coherent fiber optic bundle with a sensor array and a permanent memory with the initialized information as described is capable of faithfully reconstructing entrance pixel positions.